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NEET PHYSICSEasy

The initial velocity of a body moving along a straight line is 7 m/s7 \text{ m/s}. It has a uniform acceleration of 4 m/s24 \text{ m/s}^2. The distance covered by the body in the 5th second of its motion is:

A

25 m

B

35 m

C

50 m

D

85 m

Step-by-Step Solution

  1. Identify Formula: The distance covered in the nn-th second of uniformly accelerated motion is given by the formula: Sn=u+a2(2n1)S_n = u + \frac{a}{2}(2n - 1), where uu is initial velocity, aa is acceleration, and nn is the specific second .
  2. Alternative Method: Calculate the displacement at t=5t=5 and t=4t=4 using S=ut+12at2S = ut + \frac{1}{2}at^2 and find the difference. S(5)=7(5)+12(4)(52)=35+2(25)=85 mS(5) = 7(5) + \frac{1}{2}(4)(5^2) = 35 + 2(25) = 85 \text{ m}. S(4)=7(4)+12(4)(42)=28+2(16)=60 mS(4) = 7(4) + \frac{1}{2}(4)(4^2) = 28 + 2(16) = 60 \text{ m}.
  • Distance in 5th second =S(5)S(4)=8560=25 m= S(5) - S(4) = 85 - 60 = 25 \text{ m}.
  1. Direct Calculation: Using the nn-th second formula: S5=7+42(2×51)S_5 = 7 + \frac{4}{2}(2 \times 5 - 1) S5=7+2(101)=7+2(9)=7+18=25 mS_5 = 7 + 2(10 - 1) = 7 + 2(9) = 7 + 18 = 25 \text{ m}.
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